Handheld angle grinders are commonly used for cutting, grinding, sanding, and polishing workpieces. Due to the large diameter of the grinding disk and/or the large bias applied by the tool operator during certain tasks, the current demand by the tool from an AC power outlet can exceed the rating of the circuit breaker associated with the power outlet, thereby causing the breaker to trip. Consequently, there is a need to increase the power output of such grinders and other handheld power tools within the limits of the AC power source and without resorting to complicated and expensive power conversion circuits.
One known technique adds a capacitor to the DC bus, which lowers ripple voltage but at the same time lowers the power factor. To account for this power factor loss, it has been known to incorporate a two stage process wherein the power factor is corrected in a power factor correction circuit, which uses a feed forward signal and a feedback signal to adjust the power factor using current modulation techniques. Various techniques are set forth below for increasing power output by handheld power tools, especially ones employing a brushless electric motor, which do not require a second stage to account for power losses.
The background description provided here is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent it is described in this background section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present disclosure.